The following background information is provided to assist the reader to understand the environment in which the invention will typically be used. The terms used herein are not intended to be limited to any particular narrow interpretation unless specifically stated otherwise in this document.
It is well known that a vast majority of urban transit vehicles utilize a plurality of side mounted powered door systems for passenger ingress and egress. In some applications such as underground subways, where the transit vehicles operate in a multiple vehicle configuration and further operate in a climatically controlled environment and where the passenger generally pays first to gain access to the transit vehicle, all side door systems in every transit vehicle are being operated at every station.
In other applications, especially where transit vehicles operate above ground, the passenger may pay only upon entering the vehicle through only one side door located next to a vehicle operator while the other side doors are used predominantly for passenger egress. In such applications, it is desirable to maintain a consistent interior climatic environment of the transit vehicles for passenger comfort and minimize the effect of external environmental factors. Additionally, partially operating side door systems decreases component wear and increases durability and reliability of such side door systems. Therefore, in such applications, it is common for a vehicle operator to selectively open certain side doors while placing other side doors in a condition enabling the passenger to open such side doors by contacting a switch device mounted either directly on the side door or in its vicinity.
The well known switch devices used in such applications are touch bars and touch tape switches. U.S. Pat. No. 4,022,996 entitled “Switching Mechanism for Bus Doors with Manually Operated Touch Bar” teaches a touch bar comprising a tubular member terminated by upper and lower housings at each end that enables a small range of lateral movement in any direction. Either one or both end housings contain a switch of the electromechanical nature that is activated upon movement of the tubular member caused by the passenger contact. The resulting electrical signal is used by the door drive and door controller to open the door which then enables passenger egress.
U.S. Pat. No. 5,118,910 entitled “Illuminated, pressure-actuated switch” teaches a press-at-any-point tape switch suitable for opening doors of a transit vehicle. The switch includes a pair of electrodes which are spaced in a steady state nonactivated condition and produce an electrical signal upon pressure being applied to an exterior surface of the tape switch. The resulting electrical signal is used by the door drive and door controller to open the door which then enables passenger egress.
One disadvantage of such devices is that they contain moving components, which decrease performance reliability over time and are associated with increased manufacturing costs. Another disadvantage of such devices is that they require a pressure to be applied thereto in order to achieve activation, thus making their use more difficult for a disabled person or child.
As it can be seen from the above discussion, there is a need for an improved switch device that eliminates the use of moving components and is better suitable for use by a disabled passenger or child.
It is well known that a door system of the transit vehicle must incorporate an obstruction detection capability during the closing cycle in order to detect a passenger or an object present in the path of the closing door. Generally, the obstruction detection is accomplished by four different methods.
In a first aspect, as taught by U.S. Pat. No. 4,371,762 entitled “Contactless Pressure Sensitive Switch”, a sensitive rubber edge is employed at the leading edge of the door in combination with a pressure wave switch having an electrical connection with the door controller. The sensitivity of the rubber edge is achieved by incorporating a sealed chamber with a connection of a predetermined orifice to the pressure wave switch. The passenger or object contacting the rubber edge during the door closing cycle will deform the rubber edge thus causing the pressure differential within the seal chamber to change the state of the pressure wave switch and prevent further door closing via the door controller either terminating the closing motion or reversing the motion of the door in the opening direction.
A variation of such obstruction detection method is associated with use of an electrical tape type switch inserted into a chamber and having an electrical connection with the door controller, whereby the oppositely disposed contacts of the switch engage one another upon deformation of the rubber edge.
In a second aspect, as best taught by U.S. Pat. No. 6,064,165 entitled “Power Window or Panel Controller”, a microprocessor based door controller executes a software algorithm during door closing motion and monitors and compares parameters such as electrical current, position versus time, and others, against a predetermined threshold. The passenger or object contacting the door during the closing cycle will cause such parameters to differ from the threshold, for example the electrical current will increase, enabling the door controller to prevent further door closing.
In a third aspect, the obstruction detection may be enabled by the door controller if the door did not reach a final closing position within a predetermined time period.
In a forth aspect, as taught by U.S. Pat. No. 6,344,642 entitled “Door Control Apparatus”, the obstruction detection method employs a sensor centrally installed above the door opening and having an electrical connection with the door controller. Presence of the passenger or object will be detected by the sensor enabling the door controller to prevent further door closing.
The main disadvantage of the first three methods is that obstruction detection is enabled only upon physical contact with the passenger or object which is not desirable when such passenger is a small child or an adult with limited physical capabilities as the contact with the moving door may result in some form of injury.
Utilization of remote sensors in the fourth method eliminates physical contact but is generally costly to implement and is subject to precise tuning in order to properly define coverage area and minimize external noise.
Therefore, it is desired to implement obstruction detection that substantially minimizes or eliminates physical contact between the passenger or object and closing door and reduces installation costs.